This invention concerns a composition comprising reactive silane oligomers having low polydispersity, viscosity and volatility. Such oligomers are useful for multi-component silicon modified organic coatings with low volatile organic content (VOC), improved mar and etch resistance.
A number of clear and pigmented coating compositions are utilized in various coatings, such as, for example, automotive coatings. Such coatings, typically applied as OEM coatings (original equipment manufacturer), are generally solvent based. However, due to increasing concern over the excessive release of volatile organic component (VOC) in the atmosphere, significant research is being conducted for developing low VOC, solvent-based coating compositions, generally with less than 0.6 kilograms of organic solvent per liter of coating composition (5 pounds per gallon), as determined under ASTM D3960 Test.
One of the approaches used in reducing the amount of VOC released by a coating composition during its application on a substrate, such as an automobile body, involves adding a silicon-containing reactive diluent to the coating composition. A number of patents disclose low VOC silicon-containing curable coating compositions, such as, for example, U.S. Pat. No. 4,467,081.
However, none of the approaches disclosed in the prior art improves miscibility in multi-component formulations while still maintaining optimum balance of coating properties, such as good mar and chemical resistance, high gloss and durability. Further limiting factor in the use of silane-based reactive diluents in coating compositions is the poor process control of silane functionalities during the preparation of conventional reactive diluents, which results in a broad distribution of silane functionalities.
The present invention overcomes the foregoing problems, by providing low VOC silane-based coating compositions that result in coatings having improved mar, chemical and environmental etch resistance, appearance and durability while still providing improved miscibility in multi-component formulations, as compared to conventional coating compositions.